Over 1.8 million people worldwide were diagnosed with lung cancer in 2012. In the US, approximately 400,000 individuals are living with lung cancer and 225,000 new cases are expected to be diagnosed in 2014, comprising 13% of all cancer diagnoses. Most patients with lung cancer are elderly. In 2010, 82% with lung cancer were older than 60. It is estimated that in the US, lung cancer care costs $12.1 billion. More males are living with lung cancer than women (66.8 and 49.2 per 100,000) in the U.S., however, this difference is converging.
The survival rate of lung cancer is much lower than the other leading cancer locations, with a five-year survival rate of 16.6% compared to 64.2% for colon, 89.2% for breast, and 99.2% for prostate. More than 50% of people with lung cancer die within one year of being diagnosed. This poor survival rate has been mainly attributed to the fact that by the time a person with lung cancer becomes symptomatic, the cancer has metastasized and is in the later stages.
Recent screening programs to detect and treat lung cancer earlier have helped to improve the prognosis of people with lung cancer. The National Lung Screening Trial demonstrated that screening with low-dose computed tomography (CT) reduces mortality by 20% in certain high risk populations. Screening finds nodules sooner where they are less likely to have metastasized.
Surgery is currently the treatment of choice for patients with early stage non-small cell lung cancer (NSCLC), which can often achieve cure through the resection alone. The aim with surgery is to remove the entire tumor including a margin, typically about 2 cm of normal tissue surrounding the tumor. Different surgical approaches are commonly used, such as wedge resection, segmentectomy, lobectomy, or pneumonectomy. Which technique is used depends on the nodule characteristics, the patient's physiological reserve, and the surgeon's skill. Many of these patients have significant comorbidities and are therefore at risk of morbidity, mortality and resultant high resource utilization. Additionally, the lungs are a frequent site of metastatic disease, in 20% of cases it is the only site. Especially in patients with oligometastatic disease, surgery is part of the conventional treatment strategy. Many of these patients have high comorbidities and are non-surgical candidates.
38% of patients undergoing a resection experience major complications, including arrhythmias, prolonged air leaks, prolonged chest tube drainage and infection. A study of 7,000 patients showed a mortality rate of 1.3% for lung resections in general and 3.2% for pneumonectomies. Successful surgery often is associated with a loss of exercise capacity in the range of 10-40%, which can significantly affect quality of life. Post-resection pain can persist for four years and occurs in approximately 30% of patients. 5% of patients experience severe disabling pain. All of these complications and risk of mortality and morbidity increase in older patients and patients with comorbidities.
CT-guided percutaneous ablation in the form of radiofrequency (RF) ablation, microwave ablation, or cryotherapy are being explored as an alternative method of treating these tumors in non-surgical patients. However, none of these techniques have been successfully adapted for bronchoscopic application. Among the challenges faced by these various energy based devices is the difficulty in navigating to and penetrating the lesion, as well as the ability to take a consistent margin. In addition, these approaches are relatively lengthy (10-60 minutes per energy application) and often lead to pneumothorax. Moreover, it is difficult to ablate the entire tumor or nodule, along with a tissue margin around the tumor or nodule, with these therapies.
Condensable vapor has been delivered to the region in and around the lungs for other therapeutic purposes. For example, U.S. Pat. No. 7,892,229 describes the injection of heated water vapor into a volume of the lung distal to an occluding balloon for the purpose of shrinking and collapsing the lung tissue to reduce lung volume. The therapy results in shrinkage of collagenous tissues in the airway walls, leading to fibrosis and permanent sealing of the treated airways. The '229 patent does not address the use of condensable vapor to treat tumors or nodules in the lung, and it does not disclose how one would use the described apparatus to treat lung tumors or nodules.
U.S. Pat. Nos. 7,913,698; 8,147,532; and 8,322,335 all describe the delivery of condensable vapor to the lung to treat COPD, tumors or nodules. None of these patents describes devices or therapies specifically tailored to treat lung tumors or nodules, and none identifies a vapor delivery protocol that causes tumor or nodule tissue to necrose without also causing charring and/or thermal fixing of the tissue in and around the tumor or nodule.